These latter appear in different forms, but all are composed of a part carrying the sheets (support medium) for receiving the plots, another part supporting one or more styluses, these two parts being set in relative movement, either by moving the sheets, or by moving the styluses, or by a combination of both methods.
In these industrial plotters, the styluses depositing the ink are often either ballpoint pens, or felt tips, or else hollow tips for special inks of Indian ink type.
These styluses have several drawbacks among which may be mentioned the need of contact, during printing, between the printed medium and the stylus. Now, in the technology of the stylus and the quality of the surface of the printed medium, the quality of the plot is not constant and is not always the best, particularly when the medium to be printed is abrasive on the surface (paper . . . ), which results in a useful life of the stylus which is often very short, regardless of its technology.
Another drawback resides in the fact that the absence of printing during movement of the printed medium requires the stylus to be lifted, which results in a considerable waste of time during execution of the plot. Furthermore, on resuming the plot, the ink of the stylus does not always flow instantaneously, whence marks appear at the beginning of the plot.
A difficulty also arises as regards the compatibility between the ink, the technology of the stylus, and the quality of the medium to be printed which is not obvious and which results in greatly limiting the quality and the useful life of the plot on its medium. Generally, for each type of medium (different qualities of paper, mylar, polyester film . . . ), it is advisable to use a different type of stylus (ballpoint pens, felt tips, hollow tubes . . . ).